#!/usr/bin/env sh

# This is a wrapper script, that automatically download mill from GitHub release pages
# You can give the required mill version with --mill-version parameter
# If no version is given, it falls back to the value of DEFAULT_MILL_VERSION
#
# Project page: https://github.com/lefou/millw
#
# If you want to improve this script, please also contribute your changes back!
#
# Licensed under the Apache License, Version 2.0


DEFAULT_MILL_VERSION=0.9.5

set -e

MILL_REPO_URL="https://github.com/com-lihaoyi/mill"

# Explicit commandline argument takes precedence over all other methods
if [ "x$1" = "x--mill-version" ] ; then
  shift
  if [ "x$1" != "x" ] ; then
    MILL_VERSION="$1"
    shift
  else
    echo "You specified --mill-version without a version." 1>&2
    echo "Please provide a version that matches one provided on" 1>&2
    echo "${MILL_REPO_URL}/releases" 1>&2
    false
  fi
fi

# Please note, that if a MILL_VERSION is already set in the environment,
# We reuse it's value and skip searching for a value.

# If not already set, read .mill-version file
if [ "x${MILL_VERSION}" = "x" ] ; then
  if [ -f ".mill-version" ] ; then
    MILL_VERSION="$(head -n 1 .mill-version 2> /dev/null)"
  fi
fi

if [ "x${XDG_CACHE_HOME}" != "x" ] ; then
  MILL_DOWNLOAD_PATH="${XDG_CACHE_HOME}/mill/download"
else
  MILL_DOWNLOAD_PATH="${HOME}/.cache/mill/download"
fi

# If not already set, try to fetch newest from Github
if [ "x${MILL_VERSION}" = "x" ] ; then
  # TODO: try to load latest version from release page
  echo "No mill version specified." 1>&2
  echo "You should provide a version via '.mill-version' file or --mill-version option." 1>&2

  mkdir -p "${MILL_DOWNLOAD_PATH}"
  LANG=C touch -d '1 hour ago' "${MILL_DOWNLOAD_PATH}/.expire_latest"
  if [ "${MILL_DOWNLOAD_PATH}/.latest" -nt "${MILL_DOWNLOAD_PATH}/.expire_latest" ] ; then
    # we know a current latest version
    MILL_VERSION="$(head -n 1 ${MILL_DOWNLOAD_PATH}/.latest 2> /dev/null)"
  fi

  if [ "x${MILL_VERSION}" = "x" ] ; then
    # we don't know a current latest version
    echo "Retrieving latest mill version ..." 1>&2
    LANG=C curl -s -i -f -I ${MILL_REPO_URL}/releases/latest 2> /dev/null  | grep --ignore-case Location: | sed s'/^.*tag\///' | tr -d '\r\n' > "${MILL_DOWNLOAD_PATH}/.latest"
    MILL_VERSION="$(head -n 1 ${MILL_DOWNLOAD_PATH}/.latest 2> /dev/null)"
  fi

  if [ "x${MILL_VERSION}" = "x" ] ; then
    # Last resort
    MILL_VERSION="${DEFAULT_MILL_VERSION}"
    echo "Falling back to hardcoded mill version ${MILL_VERSION}" 1>&2
  else
    echo "Using mill version ${MILL_VERSION}" 1>&2
  fi
fi

MILL="${MILL_DOWNLOAD_PATH}/${MILL_VERSION}"

# If not already downloaded, download it
if [ ! -s "${MILL}" ] ; then
  
  # support old non-XDG download dir
  MILL_OLD_DOWNLOAD_PATH="${HOME}/.mill/download"
  OLD_MILL="${MILL_OLD_DOWNLOAD_PATH}/${MILL_VERSION}"
  if [ -x "${OLD_MILL}" ] ; then
    MILL="${OLD_MILL}"
  else
    VERSION_PREFIX="$(echo -n $MILL_VERSION | cut -b -4)"
    case $VERSION_PREFIX in
      0.0. | 0.1. | 0.2. | 0.3. | 0.4. )
        DOWNLOAD_SUFFIX=""
        ;;
      *)
        DOWNLOAD_SUFFIX="-assembly"
        ;;
    esac
    unset VERSION_PREFIX

    DOWNLOAD_FILE=$(mktemp mill.XXXX)
    # TODO: handle command not found
    echo "Downloading mill ${MILL_VERSION} from ${MILL_REPO_URL}/releases ..." 1>&2
    curl -L -o "${DOWNLOAD_FILE}" "${MILL_REPO_URL}/releases/download/${MILL_VERSION%%-*}/${MILL_VERSION}${DOWNLOAD_SUFFIX}"
    chmod +x "${DOWNLOAD_FILE}"
    mkdir -p "${MILL_DOWNLOAD_PATH}"
    mv "${DOWNLOAD_FILE}" "${MILL}"

    unset DOWNLOAD_FILE
    unset DOWNLOAD_SUFFIX
  fi
fi

unset MILL_DOWNLOAD_PATH
unset MILL_OLD_DOWNLOAD_PATH
unset OLD_MILL
unset MILL_VERSION
unset MILL_REPO_URL

exec $MILL "$@"
